Distinct ecotoxicological impairs induced by different Microcystis genotypes to Medaka fish

One of the most prevalent and notorious bloom-forming freshwater cyanobacterial genus is Microcystis, whom toxicological impairs yet remain incompletely investigated. Based on our previous studies, we hypothesize that some emerging Microcystis metabolites, in addition to microcystins (MCs), are of (eco)toxicological concerns and should be further investigated. To this end, we explore the ecotoxicological potential of different Microcystis genotypes producing various bio-active metabolite cocktails, particularly cyanopeptides of different structural families including MCs, cyanopeptolins, microginins, anabaenopetins, aeruginosins or microcyclamides, on embryo/larvae and adult Medaka fish model. Embryo and larvae exposures to the extracts of the four distinct Microcystis genotypes - comprising two MC-producing (PMC 728.11 and 807.12) and two non-MC-producing (PMC 810.12 and 826.12) strains - showed that PMC 810.12 and 826.12 respectively producing microginins, aeruginosins and microcyclamides exhibit early toxicity and teratogenicity, while PMC 728.11 presented rather larvae toxicity on hatched larvae, in agreement with its high MC content. In addition, we conducted a 4-days microcosm experiment with adult female Medaka exposed to environmental concentrations of these four Microcystis strain cultures to document the microbiome and metabolome responses. Fishes exposed to PMC 728.11 exhibited microbiota dysbiosis signature, while exposure to PMC 826.12 perturbated the fish digestion process inducing even more pronounced microbial and metabolic alterations. The two other strains provoked more moderate perturbations. These findings highlight toxic effects on fish exposed to both MC-as well as non-MC-producing cyanobacteria, suggesting complex interplay and effects of undocumented cyanobacterial bio-active and toxic compounds basides MCs during blooms of Microcystis.